1. Field of the Invention
The present invention generally relates to projectiles and, more particularly, to a fin-bearing stabilized type of projectile designed to spin; that is, to have a rolling moment.
2. Prior Art
Various types of fin-stabilized projectiles, such as missiles, bombs, marking devices, flares and the like have been provided in the past. Certain of such projectiles include fins which move from a collapsed or closed position for storage to an open or deployed stabilizing position. One such device is shown in U.S. Pat. No. 3,374,969. In that patent a projectile which can be fired from a small bore weapon is disclosed. Interlocked spring metallic vanes are held in a closed position by a gun bore and they automatically spring out to form a shrouded fin assembly, once the projectile is launched from the gun bore. The fins assume a spiral or helical configuration within the shroud. Such a device is useful for certain special small gun-fired projectiles but is complicated and impractical for larger projectiles.
A spin-cone stabilized projectile is disclosed in U.S. Pat. No. 3,081,703. Interleaved trapezoidal vanes interlocked at their edges are connected to a projectile and when the projectile is fired, they form a frusto-conical discharge nozzle fanning out behind the rear of the main projectile body and having substantial air drag. U.S. Pat. No. 412,670 is similar in that a plurality of collapsible vanes hinged at their front ends to a shell body spring outwardly when deployed to form a frusto-conical rear stabilizing array with considerable air drag.
U.S. Pat. No. 4,162,053 discloses a braking device for a rotating body such as a load-bearing vehicle ejected from projectile. The device includes curved, angled vanes or blades which extend to retard both linear and relative movement, thus providing considerable air drag.
Applicant's co-pending U.S. patent application Ser. No. 942,724 discloses a projectile with deployable fins, but no rolling moment is provided for therein.
Occasionally aerodynamic stabilizing devices are required to produce a rolling moment about the longitudinal axis of the device. This rolling moment is used to negate thrust or aerodynamic force misalignments or may be required by a target seeking guidance system. Typically a rolling moment is produced by modifying the aerodynamic surface profile, or adding aerodynamic tabs or wedges to the device. Profile modification and tabs and wedges require additional parts or manufacturing processes, which increase the cost of the device.
There remains a need for an improved type of simple, inexpensive projectile having fins which can be easily closed for storage and as easily deployed for use, which vanes flight-stabilize the projectile while importing a rolling moment to the projectile, all at little cost and with a minimum of equipment.